After reaching an above average maximum seasonal accumulation in April, Colorado’s mountain snowpack proceeded to rapidly melt across the state during May. According to data collected through the SNOTEL (SNOwpack TELemetry) network, only remnants of this winter’s snowpack remain in many of the state’s major river basins on June 1. May’s weather was slightly warmer and drier than average which, coupled with numerous layers of dust on the snowpack, has lead to a rapid depletion of the higher elevation snowpack statewide according to the USDA-Natural Resources Conservation Service (NRCS). The statewide snowpack dipped to only 32 percent of average on June 1, after recording 90 percent of average on May 1. The state’s maximum snowpack was reached on April 19th, and was 109 percent of the average maximum snowpack.

With the slightly above average snowpack during April, runoff volumes in the higher elevation streams and rivers are expected to produce near average volumes this year across much of the state. However, the impacts of the earlier than normal meltout can potentially have impacts to some water users. These impacts may be greatest during the mid to late summer demand season as streamflows recede sooner than in a typical year. In addition, those water users who are unable to rely upon upstream reservoir storage will see greater impacts from the early melt, according to Allen Green, State Conservationist, with the NRCS. In most basins across the state, snowmelt is currently ranging from about 2 to 3 weeks earlier than is typically expected for this date.

For most of the state, this summer’s water supplies are expected to be near average. However, there are several areas of the state which failed to receive enough moisture during the winter and spring to assure near average runoff volumes. Those basins include the San Juan, Animas, Dolores and San Miguel basins in southwestern Colorado. In addition, a number of other smaller basins across southern Colorado in the Rio Grande and Arkansas basins, as well as the headwaters of the South Platte River, are expected to produce below average runoff volumes this summer. For the most part, these streams are expected to flow with volumes ranging from 70 to 90 percent of average for the remainder of the summer. “For most of the state’s water users, this summer’s water supplies should be adequate, especially for those with access to upstream reservoir storage”, said Green.

Reservoir storage has increased significantly during May as the early snowmelt boosted inflows. Storage has improved to above average levels nearly statewide and is ahead of last year’s totals on this date in all basins. With statewide storage volumes at 116 percent of average, these are the best storage statistics since 1999.